Difference between gauge pressure and absolute pressure measurement

Again and again, we are asked the question about the difference between a complete pressure measurement and a gauge pressure measurement. To answer this question it helps to look at the definition of gauge pressure and absolute pressure. The difference between the two measurements is then explained relatively simply and therefore also the decision of the correct measurement.
Definition of absolute pressure
Absolute pressure is really a pressure that is relative to the zero pressure in the empty, air-free space of the universe. This reference pressure is the ideal or absolute vacuum. It is denoted with the subscript ?abs?: Pabs.
Sacred of gauge pressure
The gauge pressure is defined as the difference between an absolute pressure (Pabs) and the prevailing atmospheric pressure (Pamb). It really is denoted with the subscript ?e?: Pe and is calculated as follows: Pe = Pabs ? Pamb.
Absolute vs gauge pressure measurement
The difference between your two measurements is relatively easily clarified: in a gauge pressure measurement, it will always be the difference from the existing ambient pressure that’s measured. However, this pressure changes with the weather and the height above sea level. An absolute pressure measurement measures the difference from the ideal or absolute vacuum. For this reason this measurement is independent of environmental influences such as weather or altitude. Which measurement is currently the right one?
In practice, both measurements could be differentiated the following: in most cases, the measuring task would be to determine the gauge pressure. That is why this sort of sensor is most widely used. However, in case a gauge pressure sensor can be used in an application where the actual measuring task is to gauge the absolute pressure, the next additional errors must be expected:
+/- 30 mbar due to changes in weather
around 200 mbar when changing the positioning (e.g. from sea level to 2,000 m)
Depending on measuring range, these errors could be substantial (e.g. in pneumatics at a measuring range of 1 bar) or negligible (in hydraulics at 400 bar).
Note
For anyone who is uncertain whether your measuring task needs a complete pressure or gauge pressure measurement, simply e mail us ? we?ll be glad to assist you.

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